1. Field of the Invention
The present invention relates to an optical transmission device having accommodating structures for accommodating optical fiber cables.
2. Description of the Related Art
Optical transmission devices have recently been used not only for optical communication between telephone offices but also for optical communication in a subscriber's system which connects subscribers with telephone offices via optical fiber cables. Accordingly, it is necessary to accommodate a number of optical fiber cables in one optical communication device. The optical fiber cables have optical connectors at the ends thereof to be connected to the devices.
FIG. 10 illustrates a conventional method for accommodating superfluous lengths of optical fiber cables. The optical fiber cables are processed so that branch cables 24 extend from a main cable 22 and the lengths of the branch cables 24 from the main cable 22 are equal to each other, for connecting the branch cables 24 to an optical transmission device 100 while taking the difficulty in cutting the optical fiber cables into account. However, lengths of the branch cables from the main cable 22 to female type optical connectors 18 arranged on a back surface of a body of the optical transmission device 100 may be different from each other in accordance with the position of a respective cable holder 26 for the main cable 22. To adjust the difference in length between the respective branch cables, in the prior art, arms 102 carrying holders 104 are provided on the back surface of the body of the optical transmission device 100 to wind superfluous lengths of the branch cables 24 around the holders in a plane parallel to the back surface. This requires a larger space for the branch cables 24, extending in parallel to the back surface of the body of the optical transmission device 100.
In this method for accommodating superfluous lengths of optical fiber branch cables 24, it is necessary to take care of the problem of the space necessary for winding a number of optical fiber branch cables 24 and the problem of interference between an optical fiber branch cable and other optical fiber branch cables 24 during the mounting operation. For example, if the number of optical fiber branch cables 24 to be accommodated increases, the optical fiber cables are not fully wound around the holders 104 or, even if they could be wound, they cover the back surface of the body of the optical transmission device and disturb the connection of other cables. Also, if it is desired to remove part of the branch cables, all the optical fiber cables must be dismounted from the device and mounted again thereafter. In addition, there is a problem that the arms 102 themselves become obstacles to the connection of the branch cables 24 to the optical transmission device 100.
Methods and apparatuses which can solve these problems of superfluous lengths of optical fiber cables are disclosed in Japanese Unexamined Utility Model Publication (U.M. Kokai) No. 58-157305, Unexamined Patent Publication (Kokai) No. 58-166310 and No. 60-244906. These methods and apparatuses, however, have drawbacks that the mounting of the accommodating structures to the optical transmission device is difficult and that the requirement for the high density accommodation of cables is not satisfied.
Recently, the demand for connecting a number of optical fiber cables to an optical transmission device has increased. With this demand, problems are arising in that the optical fiber cables cannot be fully accommodated in the holders or, when it is necessary to remove some of optical fiber cables from the holders during the rearrargement thereof, all the optical fiber cables wound around the holder must be also dismounted, resulting in problems in workability and maintenance.